Geologic formations are used for many purposes such as hydrocarbon production, geothermal production and carbon dioxide sequestration. In general, formations are characterized in order to determine if the formations are suitable for their intended purpose.
One way to characterize a formation is to convey a downhole tool through a borehole penetrating the formation. The tool is configured to perform measurements of one or more properties of the formation at various depths in the borehole to create a measurement log.
Many types of logs can be used to characterize a formation. In one type of log referred to as a neutron log, a neutron source and a neutron detector are disposed in a downhole tool. The neutron source is used to irradiate the formation and the neutrons resulting from interactions with atoms of the formation are detected with the neutron detector. A formation property such as density or porosity can be determined from the detected neutrons. It can be appreciated that improving the sensitivity of the neutron detector can improve the accuracy of the formation characterization.